In modern medical practice small tissue samples, known as biopsy specimens, are often removed from tumors, lesions, organs, muscles and other tissues of the body. Such removal of tissue samples may be accomplished by open surgical technique (i.e., removal of a small sample of tissue through a small surgical incision using a local anesthetic), or through the use of a specialized biopsy instrument such as a biopsy needle. After the tissue samples have been removed, they are typically subjected to diagnostic tests or examinations such as a) gross and microscopic examination to determine cytology and/or histology, b) biochemical analyses to determine the presence or absence of chemical substances which indicate certain disease states, c) microbiological culturing to determine the presence of bacteria or other microbes, and/or d) other diagnostic procedures. The information obtained from these diagnostic tests and/or examinations can then be used to make or confirm diagnoses and/or to formulate treatment plans for the patient.
When performing an image guided biopsy procedure an obturator is used as a place holder and is placed in tissue such that its tip will be located at the point in the patient's body where the biopsy is to be taken or where a biopsy site marker or tissue marker is to be placed after a biopsy procedure. Subsequent images are acquired that can confirm the correct placement of the obturator. When the obturator is placed at the desired location within the body, blood can enter the lumen of the obturator prior to delivery of the tissue markers. This backflow of blood into the obturator creates a risk of blood clotting.
Current obturators are constructed of homogeneous materials. During magnetic resonance imaging (MRI) guided biopsies, the tip of the obturator is located by indexing through many cross sectional views (typically every 2 mm, but higher and lower discriminations are possible). The material of the obturator will be distinguishable in the cross sectional images to a varying degree depending on the morphology of the tissue and the obturator's own material makeup. Since the obturator is homogeneous, the signature of the obturator will not vary from one cross-sectional image to the next along its length. The tip of the obturator is located by selecting the first cross-sectional image in which the obturator is not seen. This result can be visually ambiguous depending on the relative strength of the image signature of the obturator compared to the surrounding tissue.
After the biopsy sample is taken, it may take several days or weeks before the results of the examination of the sample are obtained, and still longer before an appropriate treatment decision is reached. If the decision involves surgery it is clearly important for the surgeon to find the location in the breast from where the tumor tissue has been taken in the biopsy procedure, so that the entire tumor and possibly surrounding healthy tissue can be removed.
However, radiographically imageable tissue features, originally detected in a mammogram, may be removed, altered or obscured by the biopsy procedure. In order for the surgeon or radiation oncologist to direct surgical or radiation treatment to the precise location of the breast lesion several days or weeks after the biopsy procedure was performed, it is desirable that one or more biopsy site markers be placed in or on the patient's body to serve as a landmark for subsequent location of the lesion. The purpose of such markers is to facilitate the surgical procedure that is performed while the marker is detectable.
The present invention provides a marker delivery device and method for placing an obturator at the desired site in a patient's body as a placeholder and for delivering such markers into the biopsy cavity.